Omicron replicates 70 times faster in the respiratory tract than do the other forms of COVID. It seems to replicate less in the lungs. This could explain why it is more contagious but seems to cause less severe illness in many.

https://www.statnews.com/2021/12/17/prelimina...-152820318

Please note: it is worth reading the entire article, which explains clearly exactly how respiration spreads virus. This is why people need to be wearing masks whenever they are near other people, indoors or outdoors, given the huge amount of virus that infected people are breathing out.